Granted Patent
Utility
US 4,437,421 · App. 06/414,556
Variable pull off for bobbin thread
Inventor:
Ralph E. Johnson
Patented Case
View Patent ↗
Granted: Mar 20, 1984
Filed: Sep 3, 1982
Inventor
Ralph E. Johnson
Assignee (at issue)
The Singer Company Limited
This patent predates the USPTO's electronic file wrapper — prosecution documents from this era exist only in the Patent Office's paper records. A certified copy of the file history can be ordered from the USPTO's paper archives.